Memory semiconductor devices for storing data may be classified into volatile memory semiconductor devices and non-volatile memory semiconductor devices. The volatile memory semiconductor devices are typically configured to store data by charging or discharging capacitors in memory cells, and widely applied as main memories of various electronic apparatus in operation. However, the application of the volatile memory semiconductor devices is limited because the volatile memory semiconductor devices lose the stored data in the absence of power supply.
In this regard, the non-volatile memory semiconductor devices, such as flash memory semiconductor devices, have attracted the attention of many researchers. In particular, the flash memory semiconductor devices with a structure of split gates, a control gate and a memory gate, have been studied in variety of researches. The control gate selects a specific memory cell in the memory cell array. And the memory gate of the selected memory cell performs the write, erase, and read operations on the selected memory cell.
In continuous development of integrated circuit technology, the flash memory semiconductor devices with a structure of split gates confront many issues and technology difficulties in scaling-down. Among these issues and difficulties, the reliability and the uniformity defects of each memory cell are most important to be addressed. While the flash memory semiconductor device is fabricated in a scaling-down size, the reliability and uniformity may suffer serious decrease. Accordingly, improvements in methods of fabricating a flash memory semiconductor device continue to be sought.